The synthesis of ingredients for use in low unit cost consumer goods such as laundry detergents, fabric softeners, hard surface cleansers, and the like, is of considerable interest to manufacturers. Indeed, while formularies and patents are filled with listings of prospective ingredients for use in such products, the reality is that many such ingredients are simply too expensive for day-to-day use. This expense is often due either to the cost of the raw materials used to make such ingredients, or to the complex reaction and processing chemistry which is required in their manufacture. Accordingly, manufacturers have conducted a continuing search for both inexpensive raw materials and simple reaction sequences which can produce high performance, high value ingredients at the lowest possible cost.
The amido acids comprise one class of chemicals whose amido and carboxylate functional groups suggest their use as surfactants (i.e., sarcosinates), fabric softeners, antistatic agents and the like. Moreover, the amido acids constitute a basic raw material for the amido phenyl ester sulfonate class of chemicals which can serve as bleach activators in laundry detergents and other types of bleach-containing cleaning compositions. Such activators have several desirable attributes such as excellent bleaching performance with minimal color damage on fabric dyes, good washing machine compatibility and a good odor profile in the wash. On the positive side, the amido acids and their aforementioned derivatives are potentially obtainable from inexpensive raw materials. Unfortunately, the synthesis of certain amido acids is somewhat complicated and can involve the use of solvents, with additional problems associated with recycle streams and the like. Problems can also arise with the formation of undesirable colored by-products. Moreover, the conversion of the amido acids to their phenyl ester form is not straightforward and can be surprisingly problematic.
The present invention provides a simple, one-step method for the synthesis of amido acids. It also provides four methods for converting amido acids into amido acid phenyl ester sulfonates which are suitable for use as bleach activators in laundry detergents, and the like. The first method is a simple, one-step esterification of amido acid with phenol to provide an amido acid phenyl ester which can subsequently be reacted with SO.sub.3 and neutralized in conventional fashion to give amido acid phenyl ester sulfonates. The second prepares the amido acid phenyl ester by transesterification of ester derivatives of phenol followed by the conversion to the amido acid phenyl ester sulfonates as described for the first method. The third method involves transesterification of ester derivatives of phenol sulfonic acid or salt, preferably acetoxybenzenesulfonic acid or salt (typically sodium or potassium), with amido acid to provide amido acid phenyl ester sulfonates directly. The fourth method involves making the anhydride of the amido acid and reacting this anhydride with sodium phenolsulfonate to also produce amido acid phenyl ester sulfonate directly.
The individual reaction sequences herein proceed in acceptable yields (typically 60%, and higher) and, importantly, result in products with minimal discoloration. The reactions may be conducted without added solvents, i.e., the reactants act as solvents. Hence, for many purposes the reaction products need not be extensively purified which further improve the overall economics of the processes.